Piper and Phoebe Halliwell are devastated by the loss of their big sister, Prue. But even in their grief they can't forget that they, too, are in mortal danger. The power of the Charmed Ones has been broken, leaving them prey to every form of evil. Even Leo, their Whitelighter, and Cole, Phoebe's demon boyfriend, can't protect them.

In frustration and despair, Piper casts a spell to summon a lost witch and bring back her beloved Prue. The spell does work, but not as Piper intended. A lost witch is found - heir to a shocking Halliwell family secret. But can Piper and Phoebe persuade her to assume her powers and complete the Power of Three?